Minimal Residual Disease (MRD) Status in FCR-Treated CLL Patients at the End of Treatment Influences Progression Free Survival (PFS), Results of the Ctrial-IE (ICORG) 07-01/ CLL Ireland Study, with Mutational Analysis Providing Additional Insight

Fludarabine, cyclophosphamide and rituximab (FCR) therapy results in a complete remission (CR) rate of 72% and a median progression free survival (PFS) of 80 months in non-del (17P) CLL1. Achieving an MRD negative (MRD-ve) CR after completing therapy is an early surrogate marker for overall survival (OS) and PFS2. Specific genetic CLL subtypes determined by fluorescent in-situ hybridisation (FISH) analysis, immunoglobulin mutation IgVH, NOTCH1 and SF3B1 status determine response to chemotherapy3,4. We completed a multi-centre prospective study between 2008 and 2012, with a median follow up of 62.6 months using MRD status to determine length of therapy. Patients who achieved an MRD-veCR after 4 courses of FCR received no further therapy and the remaining patients completed 6 cycles of FCR. MRD status was tracked 6 monthly in patients who became MRD-veuntil MRD was detected. The genetic subtype was also analysed but did not influence treatment. Fifty-two patients {35M;17F, median age 61years (range 37-73)} were enrolled. Forty-six patients completed the MRD assessment after 4 cycles. Eleven patients discontinued assigned FCR therapy for the following reasons: prolonged cytopenia (4); non-compliance (1); autoimmune haemolytic anaemia (2); renal impairment (1); pleural effusion (1); not recorded (2). Eighteen (34.6%) patients achieved an MRD-veCR after 4 cycles and a further11 after 6cycles resulting in 29/52 (55.8%) MRD-veCRs in total. The median PFS was 72.3 months (95% Confidence Interval 61.3-84.1 months) and the median OS has not been reached. Patients who attained an MRD-veversusMRD+vestatus had a prolonged PFS (81.1 vs 46.2 months, p<0.0002). No difference in PFS was observed between patients reaching an MRD-veCR after 4 versus 6 cycles (median PFS81.1 vs 84.1 months,p=0.29). FISH results were available for 48 patients; del(13q) in 16/48 (33%), del(11q) in 15/48 (31%) no abnormality in 12/48 (25%), trisomy 12 in 4 (8%) and other abnormality in 1 patient. The IgVH status was unfavourable in 34/52 (65%), SF3B1 mutations were detected in 5/51 (9.8%) and NOTCH1 mutations in 10/52(19.2%) patients respectively, comparable to published studies of first-line treatment in CLL3,4. The median PFS for patients with good risk IgVH was not reached. Del(11q) did not impact on PFS (median PFS 66.5 vs 78.9 months, p=0.7301). SF3B1 and NOTCH1 mutated patients had a shortened PFS (median PFS 38.4 vs 71.1 months, p=0.038 and median PFS 62.4 vs 82.2 months p=0.0302, respectively). In conclusion abbreviated FCR therapy is effective for patients achieving MRD-veremission after 4 cycles. SF3B1 and NOTCH1 mutated patients had a short PFS and may benefit from alternative first-line treatment. This finding emphasizes the role mutational profiling will play in optimising and personalising therapy in CLL in the future. Reference: Tam C, O'Brien S, WierdaW, et al. “Long-term results of the fludarabine, cyclophosphamide and rituximab regimen as initial therapy of chronic lymphocytic leukemia” Blood 2008 Aug 15;112(4):975-80 Böttcher S, Ritgen M, Fischer K, et al. "Minimal Residual Disease Quantification is an Independent Predictor of Progression-Free and Overall Survival in Chronic Lymphocytic Leukemia: A Multivariate Analysis From the Randomized GCLLSG CLL8 Trial" J Clin Onc 2012 Mar 20; 30(9):980-8. StilgenbauerS,SchnaiterA,PaschkaP, et al. "Gene mutations and treatment outcome in chronic lymphocyticleukemia: results from the CLL8 trial" Blood 2014 May 22;123(21):3247-54 Chiaretti S, Marinelli M, Del Giudice I, et al."NOTCH1, SF3B1, BIRC3 and TP53 mutations in patients with chronic lymphocytic leukaemia undergoing first-line treatment: correlation with biological parameters and response to treatment"LeukLymphoma 2014 Dec; 55(12):2785-92 Figure 1 Patient outcomes by MRD status in ICORG 07-01 Trial Figure 1. Patient outcomes by MRD status in ICORG 07-01 Trial Figure 2 Figure 2. Figure 3 Figure 3. Disclosures Crotty: BMS, Takeda, Novartis, Janssen, Roche: Honoraria. O'Dwyer:Glycomimetics: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding.